Splice case with gas tight seal

ABSTRACT

A gas tight seal for a communication cable splice case to withstand high and low temperature cycling and suitable for installation in the field. A split case with a resilient grommet at each end in compressive engagement with the case and cable, with the grommet oversize in the dimension perpendicular to the case flanges and having interior cavities for internal deformation of the grommet when compressed by the closing of the case urging the grommet into sealing engagement with the case and with the cable.

United States Patent 1 [111 3,796,823

Wright et al. Mar. 12, 1974 [54] SPLICE CASE WITH GAS TIGHT SEAL fi fi iEiiifiihEiJfiiirflfTICIaSi' 75 Inventors; James A, w Ja M, 5254 2124525,ei,f? v?:fiit izle l rl flifmf id Kosmala, both of Allegany, N.Y.Tmsley [73] Assignee: The Dexter Corporation, Olean, i n H v s7 7ABSTRACT [22] Filed: June 6, 1972 A gas tight seal for a communicationcable splice case [21] App! 260224 to withstand high and low temperaturecycling and suitable for installation in the field. A split case with a[52 US. Cl. 174/92, 174/77 R, 277/227 resilient grommet at each end incompressive engage- 51 Int. Cl H02g 15/03 ment with the ease and cable,with the grommet ever- [58] Field of Search 174/91-93, Size in thedimension Perpendieuler to the ease flanges 174/77 R 33 R 153 G, 152 G,5 77 227 and having interior cavities for internal deformation of thegrommet when compressed by the closing of the [56] References Ci d caseurging the grommet into sealing engagement with UNITED STATES PATENTSthe case and with the cable.

3,337,681 8/1967 Smith 174/93 X 12 Claims, 7 Drawing Figures FOREIGNPATENTS OR APPLICATIONS 24,441 1914 Great Britain 174/152 G BACKGROUNDOF THE INVENTION This invention relates to the splicing ofmulticonductor communication cables, typically telephone cables, andmore particularly to an assembly for providing a gas tight seal for thesplice casing.

A typical communication cable may contain a large number of smallconductors with appropriate electrical insulation and an outer metalsheath and be in the order of one inch diameter. Two or more cables arespliced by exposing individual conductors thereof and making electricalconnections therebetween. After the splicing is completed, the splicezone is enclosed in a case for protection and a typical splice case isshown in US. Pat. No. 3,614,298. Splice cases of this type have been inuse for a long time and comprise mating half tubular sections which arebolted together at flanges providing an open interior for the splicedcables and providing access openings at each end for the cables. Someform of seal is provided about the cables at each access opening and theinterior of the case is charged with a gas at about psi to prevent entryof moisture into the case. Therefore the seals should be gas tight andshould maintain the sealing integrity over the wide temperaturefluctuations encountered in the field, typically from -40 to +140Fahrenheit and through the variety of mechanical stress introduced bycable flexing and the like.

Two approaches have been utilized in sealing the splice cases. In onearrangement, lead sheaths are sweated or forged on the cables, leadrings are positioned between the cables and the case, and after the caseis bolted together, the assembly is caulked with molten lead.

In another approach, the cables are wrapped with a tape or cord to fillthe space between the cable and case and this structure is soaked withan adhesive to bond the elements together. Several variations of thisapproach are shown in the aforementioned US. Pat. No. 3,614,298 and US.Pat. Nos. 3,148,241, 2,771,502 and 3,061,666.

While some of these prior configurations have met the requirement of agas tight seal, they are diffucult to produce, particularly in thefield, and require considerable time and expertise to obtain the desiredgas tight condition over the operating extremes.

It is often required that a splice case be opened, the conductorconnections be changed, and the case be resealed in the field. The priorart seals have been particularly troublesome to the field worker becauseof the problems of removing the remnants of the old seal from the cableand the case halves prior to preparing the new seal. Furthermore,forging lead sheaths and handling molten lead is a difficult operationin the field, in addition to the fact that the metal-to-metal jointbetween the lead sealing material and the iron or aluminum case issubject to great stress during temperature changes. Similarly, thecleaning out of the adhesive loaded wrapped tape or mastic packed sealand the installation of a fresh seal is expensive and sometimesuncertain under field conditions.

Accordingly, it is an object of the present invention to provide a newand improved splicing assembly for a communication cable using theconventional split case and a seal for each access opening in the formof a single unitary factory produced elastomeric grommet with the cablepositioned therein and with the gas tight sealing being accomplished bythe clamping action of the case halves compressing the uniquelyconfigured grommet into sealing engagement with the case and cable. Sucha seal will not require lead sweating or casting or adhesive soaked tapeor mastic.

SUMMARY OF THE INVENTION gas under pressure into the interior of thecase. A unitary elastomeric grommet is positioned in each of the accessopenings, with the periphery of the grommet in engagement with the caseand with the configuration of the periphery of the grommet generallydictated by the configuration of the case opening. One or more passagesare provided through the grommet for the cable. Preferably each passagehas a plurality of ridges of inside diameter less than the outsidediameter of the cable to provide a gripping engagement with the cable.The cable is inserted into the passage through a slit in a thick wallsection of the grommet, and cavities are provided in the inner face ofthe grommet on opposite sides of the cable passage. The grommet has adimension perpendicular to the plane of the flanges of the case sectionsgreater than the diameter of the case access opening. In use, the cablesare positioned in the grommets and the cable and grommet assembly ispositioned in a case half section. The other case half section is placedin position and the case sections are bolted together. The clampingaction of the case compresses the grommet about the cable, compressesthe grommet along the dimension perpendicular to the plane of theflanges providing tight engagement between the grommet and case, andprovides compression forces at the slit faces, with the cavitiesproviding for internal deformation of the resilient grommet. A flexiblesealing compound may be provided at the case-grommet and grommet-cableinterfaces and at the slit faces. The resultant assembly meets therequirements for a gas tight seal and successfully passes thetemperature cycling tests specified by the telephone companies.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an interior view of aconventional splice case half section;

FIG. 2 is an end view of a grommet for a splicing assembly,incorporating the presently preferred embodiment of the invention;

FIG. 3 is an end view of a splicing assembly showing the case, grommetand cables in position;

FIG. 4 is a sectional view taken along the line 4-4 of FIG. 3;

FIG. 5 is a sectional view taken along the line 55 of FIG. 4; and

FIGS. 6 and 7 are views similar to FIG. 3 illustrating steps in theassembly of the case.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The splice case is formed ofsplit sections 10, 11 joined along flanges 12, l3, 14, 15 by bolts 16,and nuts 17 to provide a large central splice zone 20 and reduced endswith access openings 21.

A grommet is provided for each access opening, with one or more cables26 passing through each grommet. A cable splice may require one cablefrom each end of the case or two cables at one end and one cable at theother end or two cables at each end, depending on the telephone companysrequirements. Grommets with a single cable opening and grommets with twoor more cable openings can be utilized as required.

The grommet 25 is a single unitary elastomeric unit typically molded ofurethane or other suitable plastic which will maintain its elastomericqualities over the desired temperature operating range. The periphery ofthe grommet may have a configuration which corresponds with theconfiguration of the access opening of the case, typically comprisingarcuate ridges 30 and grooves 31 with a shoulder 32 adjacent the innerface 33 and a shoulder 34 and flange 35 adjacent the outer face 36. Theridges 30 and grooves 31 are not circumferential, being interrupted bylongitudinal ridges 40, 41 diametrically opposite each other on theperiphery of the grommet. In the subsequent discussion, the ridge isarbitrarily referred to as the top of the grommet and the ridge 41 thebottom.

The ridges 40, 41 engage corresponding grooves in the case sections andprovide for rotational alignment of the grommet in the case. The ridges30 and grooves 31 and the shoulders 32, 34 engage corresponding elements in the case and lock the grommet in place against axial movementin the case. Alternatively the periphery of the grommet may be smoothand engage the case only at the case opening ridges.

Cable passages 45, 46 are provided through the grommet 25. Each cablepassage desirably issIightly smaller than the cable to be positionedtherein and in the embodiment disclosed, each passage contains aplurality of circumferential ridges 47 disposed along the passage forengagement with the cable, with the ridges being deformed slightly whenclamped into engagement with the cable as will be described below.

Slits 48, 49 through a thick wall section 50 of the grommet provideaccess for sliding the cables into the passages 45, 46, respectively.The slit is a potential gas leakage path and the slit location isselected to provide optimum slit closing forces when the grommet isclamped in position in the case. The dimension of the grommetperpendicular to the plane of the case flanges is made greater than thediameter of the case access opening by a few percent, typically about 2percent. Preferably the grommet is elliptical in cross section with amajor axis 52 anda minor axis 53, with the major axis perpendicular tothe plane of the case flanges and with the cable passages 45, 46 onopposite sides of the minor axis 53. Alternatively, the grommet can becircular in cross section with the grommet diameter greater than theopening diameter by a few percent. When the case halves are clampedtogether, the grommet is com- I pressed across the major axis andcompression forces are produced at the faces of the slits 48, 49.

The specific location of the slits 48, 49 may vary and the specificorientation of the slits may vary, but the slits should be in the thickwall section as at 50, rather than in a thin wall section as at 55. Thepreferable angular location for the slits is that shown ,in FIG. 2,where the plane of the slits is oblique to the plane of the minor axis53 and at an angle such that the compression forces at the slit facesresulting from compression of the grommet along the major axis, aresubstantially perpendicular to the slit faces, which configurationprovides the optimum sealing and minimum opportunity for gas leakage.

It is preferred that the minor axis 53 be smaller than the diameter ofthe case access opening by a few percent, typically about two percent.With this relationship, the grommet is more easily placed in position ina case half. As the case halves are clampedtogether compressing thegrommet along the major axis, it can expand along the minor axis toprovide complete sealing engagement on the periphery of the grommet.

Cavities 60, 61 are provided in the thick wall sections of the grommeton opposite sides of the cable passages 45, 46. The thick wall sectionsare generally T-shaped and the cavities preferably have the sameconfiguration, as shown in FIG. 5. The cavities are formed in the innerface 33 and extend toward the outer face, typically at least half wayfrom the inner face toward the outer face. In the single cableconfiguration, the cable passage may be centrally located in the grommetwith the slit along the minor axis and with a pair of arcuate cavitieson opposite sides of the cable passage. In operation, the cavitiespermit internal deformation of the grommet when it is compressed byclamping in the case. Without this internal deformation capability,buckling is likely to occur along the periphery of the grommet creatingpotential gas leakage paths between the grommet and case.

In assembling the splice case after the splicing has been completed,strips 65, 66 of conventional sealing tape are positioned in the groovesof the conventional case section 10. A grommet is selected for each endand the cables are inserted into the grommet through the slits. Thegrommet and cable assembly is then placed in the case section 10 with agrommet at each end of the case section and engaging the mating ridgesand grooves. The other case section 11 is laid down on the first casesection and the bolts are inserted and tightened along the lowerflanges, as seen in FIG. 6.

Bolts are inserted and tightened along the upper V flanges, bringing thecase to the condition of FIG. 7. The lower bolts are again tightened tothe condition of FIG. 3 and the upper bolts are then tightened. A thinlayer of a flexible sealing compound 70 can be applied along thecase-grommet interfaces and the cablegrommet interfaces and the grommetslit faces to improve the gas sealing capability (FIG. 5). Varioussealing compounds on the market can be used. Urethane base compoundswhich operate over the temperature range of -40 to +F. are preferred.

When the case is clamped on the grommets, the grommets are compressedalong the major axis and expand along the minor axis bringing theperiphery of the grommet into tight sealing engagement with the casesections. The grommet is also compressed about the cable in each of thecable passages, bringing the ridges 47 into engagement with the cableand deforming the ridges somewhat to provide a tight seal betweengrommet and cable. The grommet compression also produces compressionforces at the slit faces producing a gas tight seal along the slits. Thecavities permit internal deformation of the grommet resulting from thecompression forces without producing buckling at any of the interfaces.

The case tightening procedure wherein the bottom flanges are tightenedahead of the top flanges insures proper closing of the slit and preventsmismating of the slit faces during the clamping operation.

The splicing assembly of the present invention provides a useable gastight seal for the communication cable field. By way of example, asplicing assembly with a conventional cast iron split case having threeand one-half inch diameter access openings and two one and one-quarterinch lead sheathed cables exiting at each end and a molded urethanegrommet installed with a flexible sealing compound has successfullypassed temperature cycling tests. The case was charged with nitrogen atplug 68 to psi and the assembly was cycled from 40 F. to 140 F. and backevery 8 hours for 100 cycles without gas leakage.

The unitary grommet is easily and quickly installed in the field andprovides a substantially fool-proof arrangement for making a gas tightseal in a splicing assembly. The factory produced grommet seal isparticularly advantageous where a sealed case is to be opened for achange in electrical connections and then resealed. The originalgrommets are readily removed, the case does not require any extensivecleaning operations, and the case is readily sealed again after theelectrical connections have been revised.

We claim:

1. In a splicing assembly of multiconductor sheathed communicationcables, the combination of:

a split case enclosing a cable splice and including first and secondhalf tubular sections with mating flanges along upper and lower edges,means joining said sections at said flanges, defining cylindrical accessopenings at each end of said case, and means for introducing gas underpressure into said case;

a single unitary elastomeric grommet positioned in each of said accessopenings,

at least one of said grommets having an inner face and an outer face andat least two cable passages therethrough, a slit through a thick wallsection between the cable passages and the periphery, a dimensionperpendicular to the plane of said flanges greater than the accessopening diameter, and cavities in said inner face on opposite sides ofsaid cable passages and extending part way toward said outer face;

a thin layer of flexible sealing compound at the slit faces and at theinterfaces of the case sections and grommets and at the cable sheathsand grommets;

with said case sections joined at said flanges clamping each of saidgrommets in said case, compressing the grommets and clamping thegrommets on the cable sheaths and producing compression forces at thefaces of the slits maintaining a gas tight seal between case and cable.

2. An assembly as defined in claim 1 wherein each of said grommets andsaid case have interengaging elements axially locking the grommet in thecase.

3. An assembly as defined in claim 1 including a plurality ofcircumferential grooves in the wall of the cable passages definingdeformable ridges between the grooves engaging the cable sheath insealing relation.

4. An assembly as defined in claim 1 wherein said cavities are centrallypositioned in and have the configuration of the thick wall section ofthe grommet.

5. An assembly as defined in claim 1 with two cable passages in thegrommet spaced from each other along said major axis defining generallyT-shaped thick wall sections adjacent the upper and lower edges of saidcase.

6. An assembly as defined in claim 5 wherein said cavities are generallyT-shaped and are in said T- shaped wall sections.

7. An assembly as defined in claim 6 wherein said cavities extend atleast half way from said inner face toward said outer face.

8. An assembly as defined in claim 5 wherein the slits are in arms ofthe T-shaped wall sections.

9. An assembly as defined in claim 5 wherein each of the slits isadjacent a cavity.

10. An assembly as defined in claim 5 wherein each of the slits is in aplane oblique to the plane of said flanges at an angle such that thecompression forces at the slit face are substantially perpendicular tothe face.

11. An assembly as defined in claim 1 including opposed ridges at theperiphery of the grommet parallel to the longitudinal axis of the caseand engaging mating grooves in the case rotationally aligning of thegrommet in the case.

12. In a splicing assembly of multiconductor sheathed communicationcables, the combination of:

a split case enclosing the cable splice and including first and secondhalf tubular sections with mating flanges along upper and lower edges,means joining said sections at said flanges, defining cylindrical accessopenings at each of said case, and means for introducing gas underpressure into said case; and

a single unitary elastomeric grommet positioned in each of said accessopenings, each of said grommets and said case having interengagingelements for axially locking the grommet in the case,

at least one of said grommets having an inner face and an outer face andat least two cable passages therethrough, a slit through a thick wallsection between the cable passages and the periphery, and cavities insaid inner face on opposite sides of said cable passages and extendingpart way toward said outer face generally parallel with said cablepassages, each of said cable passages having a substantially uniformdiameter throughout its length,

with said case sections joined at said flanges clamping each of saidgrommets in said case, compressing the grommets and clamping thegrommets on the cable sheaths along the lengths of the cable passagesand producing compression forces at the faces of the slits maintaining agas tight seal between case and cable.

1. In a splicing assembly of multiconductor sheathed communicationcables, the combination of: a split case enclosing a cable splice andincluding first and second hAlf tubular sections with mating flangesalong upper and lower edges, means joining said sections at saidflanges, defining cylindrical access openings at each end of said case,and means for introducing gas under pressure into said case; a singleunitary elastomeric grommet positioned in each of said access openings,at least one of said grommets having an inner face and an outer face andat least two cable passages therethrough, a slit through a thick wallsection between the cable passages and the periphery, a dimensionperpendicular to the plane of said flanges greater than the accessopening diameter, and cavities in said inner face on opposite sides ofsaid cable passages and extending part way toward said outer face; athin layer of flexible sealing compound at the slit faces and at theinterfaces of the case sections and grommets and at the cable sheathsand grommets; with said case sections joined at said flanges clampingeach of said grommets in said case, compressing the grommets andclamping the grommets on the cable sheaths and producing compressionforces at the faces of the slits maintaining a gas tight seal betweencase and cable.
 2. An assembly as defined in claim 1 wherein each ofsaid grommets and said case have interengaging elements axially lockingthe grommet in the case.
 3. An assembly as defined in claim 1 includinga plurality of circumferential grooves in the wall of the cable passagesdefining deformable ridges between the grooves engaging the cable sheathin sealing relation.
 4. An assembly as defined in claim 1 wherein saidcavities are centrally positioned in and have the configuration of thethick wall section of the grommet.
 5. An assembly as defined in claim 1with two cable passages in the grommet spaced from each other along saidmajor axis defining generally T-shaped thick wall sections adjacent theupper and lower edges of said case.
 6. An assembly as defined in claim 5wherein said cavities are generally T-shaped and are in said T-shapedwall sections.
 7. An assembly as defined in claim 6 wherein saidcavities extend at least half way from said inner face toward said outerface.
 8. An assembly as defined in claim 5 wherein the slits are in armsof the T-shaped wall sections.
 9. An assembly as defined in claim 5wherein each of the slits is adjacent a cavity.
 10. An assembly asdefined in claim 5 wherein each of the slits is in a plane oblique tothe plane of said flanges at an angle such that the compression forcesat the slit face are substantially perpendicular to the face.
 11. Anassembly as defined in claim 1 including opposed ridges at the peripheryof the grommet parallel to the longitudinal axis of the case andengaging mating grooves in the case rotationally aligning of the grommetin the case.
 12. In a splicing assembly of multiconductor sheathedcommunication cables, the combination of: a split case enclosing thecable splice and including first and second half tubular sections withmating flanges along upper and lower edges, means joining said sectionsat said flanges, defining cylindrical access openings at each of saidcase, and means for introducing gas under pressure into said case; and asingle unitary elastomeric grommet positioned in each of said accessopenings, each of said grommets and said case having interengagingelements for axially locking the grommet in the case, at least one ofsaid grommets having an inner face and an outer face and at least twocable passages therethrough, a slit through a thick wall section betweenthe cable passages and the periphery, and cavities in said inner face onopposite sides of said cable passages and extending part way toward saidouter face generally parallel with said cable passages, each of saidcable passages having a substantially uniform diameter throughout itslength, with said case sections joined at said flanges clamping each ofsaid grommets in said case, compressing the grommets and clampiNg thegrommets on the cable sheaths along the lengths of the cable passagesand producing compression forces at the faces of the slits maintaining agas tight seal between case and cable.